Process of making metal alkyls



Feb. 21, 1939: F. w, SULLIVAN. JR 2,148,138

PROCESS OF MAKING METAL ALKYLS Filed Aug. 31, 1936 #eacf/bn 66477756!" 6INVENTOR Freder/ck NSu/hvaqdr ATTORNEY Patented Feb. 1939' PATENT OFFICE2,148,138 mocnss OF MAKING METAL ALKYLS' Frederick W. Sullivan, Jr.,Flossmoor, Ill, assignor to Standard Oil Company, Chicago, Ill., acorporation of Indiana Application August 31, 1936, Serial No. 98,711

14 Claims.

This invention relates to processes of preparing organic compounds oflead and it comprises processes wherein a hydrocarbon such as methane,ethane, propane, butane, pentane, hexane, and

hydrocarbons occurring in gasoline, are dissociated by-the action ofhighly heated lead vapors and/or atomic hydrogen to form free alkylradicals from such hydrocarbons, the resulting reactionmixturecontaining free alkyl radicals quick- 1y cooled and reacted with lead toform hydrocarbon compounds of lead.

In my United States Patent 'No. 2,087,660, issued July 20, 1937, ofwhich the present application is a continuation-in-part, I havedisclosed methods of making hydrocarbon compounds of lead whereinmetallic lead, in solid form, is caused to react with a hydrocarbon gascontaning free alkyl radicals. As described in that application thereaction products can be condensed, or they can be absorbed in anabsorbent oil to recover the lead hydrocarbon compounds as such. Or, asdescribed in that application, I can leadize gasoline, by subjecting thegasoline to pyrolytic condit ons which result in the formation of somefree alkyl radicals therein, react thes radicals with metallic lead, andcondense a final product containing a small amount of lead-hydrocarboncompounds dissolved in a large volume of gasoline.

I have now discovered that the broad processes of said application canbe improved as regards economy of operation, conservation of energy fordissociating the hydrocarbon material, and impound. I have nowdiscovered that I can use the heat inherent in vaporized lead topyrolytically dissociate the hydrocarbon starting material. I

have discovered that this method of initially forming quantit es of freealkyl radicals gives me higher yields of final products. Thus, forexample, in broad aspects, I first vaporize lead at very low absolutepressures, generally about to 4 mm. of mercury, and rarely exceeding 30to 50 45 mm. of mercury. Although lead boils at atmospheric pressure ata temperature of about 27'70 F., at a pressure of from to 4 mm. theboiling point is reduced markedly. Generally the boiling point under myconditions of low pressure varies from about 1800 to 2000 F.

Lead vapor at ths temperature and a e low pressure stated is thencontacted with hydrocar bon vapor and the resulting mixture of reactionproducts is immediately and quickly cooled to 55 temperatures below thedecomposition-tempera- -will react with lead to form lead alkyls.

provement in yield of lead hydrocarbon comture of lead hydrocarboncompounds. This temperature does not generally exceed about 150 C. Thereaction products are then condensed and, if desired, hydrocarboncompounds of lead recovered therefrom. 5

There are many advantages in this procedure. Other things being equal,the yield of lead alkyls, such as tetraethyl lead, is dependent upon thequantity and physical form of lead associated with the free alkyls atthe time of cooling. When 10 free alkyls, such as methyl or ethyl, areformed in the presence of lead, the alkyls can react in two differentways. They can either react with themselves or with the lead. But tosecure high yields of lead compounds, the lead should be present in 15intimate association with the gaseous mixture which contains the alkyls.Then, as this mixture is quickly cooled down to a temperature at whichlead alkyls are stable, the lead is immediately available for reactionwith the free alkyls. 20

The alkyl-yielding hydrocarbons can also be dissociated by means ofatomic hydrogen to give gaseous mixtures containing free alkyls whichThis method of forming free alkyls is particularly ad- 25 vantageous andcan be employed alone or in combination with the lead vapor thermalmethod of free radical formation. 1

On the attached sheet of drawngs I have indicated in flow-sheet form,apparatus arrange- 30 ments which can be used to practice the processesof the present invention. In the drawing I have shown suitable apparatusfor dissociating hydrocarbons by means of lead vapors and to react thefree alkyls with lead and. recover the reaction 35 products.

Referring to the drawing the numeral I indicates an electric arc furnacehaving an inlet 2 for charging the furnace with lead. Current leads areshown at 3 and 4 and the electrodes at 5. The body of molten leadisindicated at 6.

Lead vapors resulting from the heat developed by the electrodes leavethe furnace through outlet I which conducts them to the reaction chamberI. This reaction chamber is composed of three zones 9, l0 and I I. Zone9 is provided with a baflie l2 and hydrocarbon inlet l3 through whichvaporized or normally gaseous hydrocar bons enter the system. Zone I0 isa cooling zone containing a cooling coil l4 supplied with a suitablerefrigerant such as brine, liquefied gases and the like. Zone II is alsokept cool by a water H jacket 5.

Cooling coils H are constructed of a suitable metal and zone 9 has heatinsulating material It to reduce condensation of vaporized lead thereinand if desired, it may be externally heated to prevent condensation. Anylead which does condense on the walls of zone 9 can be returned to thefurnace through pipe I1.

Reaction products leave the zone II through outlet I8 leading to acondenser or cooler I9 which discharges through pipe 20 into areceptacle for lead alkyls 2I. Any uncondensed vapor passes through 22to a pump 23 where it is pumped back to inlet I3 through line 24assisted by a suitable pump 32 if desired. Some of this vapor can be ledinto the furnace I through line 25 to aid in the vaporization of thelead. If desired, it may be bubbled beneath the surface of the lead, andthe bath may be heated by an electric induction furnace.

The uncondensed vapor can alternatively be passed through absorber 26 byvacuum pump 21 and line 28, where it may be drawn off overhead throughline 30. Absorber 26 is supplied with a high-boiling hydrocarbon liquidsuch as absorber oil. Vacuum pump 21 maintains the necessary lowpressure on the system and circulating pump 23 provides for recyclinguncondensed gas. Alternatively, the uncondensed vapor may be passedthrough valved line 3| and recycled through line 24 if desired.

In the operation of the arrangement shown in the drawing the furnace ischarged with lead, current applied and vacuum pump 2! is started tomaintain the system under a pressure of about to 4 mm. of mercuryabsolute pressure. Care should be taken that all joints are airtight sothat no air can enter the system. When lead vapors begin to distill fromretort I and pass into zone 9 of reactor 8 hydrocarbon vapors areallowed to flow into zone 9 through inlet I3. As pointed out above,these hydrocarbon vapors are generally aliphatic hydrocarbons, althougharomatic hydrocarbons can be used, provided they are heated suflicientlyto be dissociated to yield free radicals which are capable of combiningwith lead. For most practical purposes I find that an ordinary gasolinefraction is advantageously used. I can, however, use propane, butane, orother low boiling hydrocarbons.

To prevent excessive condensation of metallic lead on the surfaces ofzone 9 it is desirable that this zone be well insulated against loss ofheat or auxiliary heating provided, and this is why I provide heatinsulating covering I6. Likewise, it is preferred to preheat thehydrocarbon vapors admitted at I3 to a temperature of 750 to 1100 F. byany suitable means such as a heating coil not shown. The averagetemperature of zone 9 is in the neighborhood of 2000 F. This is highenough to insure that the introduced hydrocarbons decompose ordissociate instantly to give commercially useful quantities of freealkyl radicals. The velocity of the gases passing through reactionchamber 8 is exceedingly rapid due to the action of pumps 23 and 21 andcondensation and cooling of vapors in condenser I9. It is essential thatthe hot gases composed of lead vapors and free alkyl radicals togetherwith undecomposed hydrocarbons are passed quickly into contact withcooling coils I4. The cooling coils are operated at temperatures ofabout minus C. to plus 100 0., depending upon the refrigeranttherein'and also upon the specific lead alkyl compounds produced. It isdesirable to keep the cooling coil temperature above the boilingtemperature of the lead alkyl product at the pressure employed. Thus,for lead tetraethyl film on cooling coils I4.

and a pressure of 3 mm. of mercury, the cooling coil temperature shouldbe above 30? F. Consequently, the gases from zone 9 are quickly cooleddown to temperatures below the decomposition temperature of thelead-hydrocarbon compounds. In zone II] the lead vapor almostinstantaneously condenses either as a fog or mist of solid or liquidlead particles or as a thin Concurrently the free alkyl radicals reactwith the lead to form leadhydrocarbon compounds. The mixture flowingfrom zone In into zone I I now contains hydrocarbon compounds of leadand unreacted hydrocarbon. Advantageously zone II is provided withcooling jacket I5 to keep the mixture therein Well below thedecomposition temperature of lead alkyls. The temperature of the vaporsleaving zone II is generally about 100 to 140 C. The mixture then flowsto condenser I9 where hydrocarbon vapors and hydrocarbon compounds oflead are condensed and collected in receiver 2|.

The life of the free alkyl radicals formed in zone 9 is limited.Ordinarily these free radicals exist for less than about one tenth of asecond. and consequently it is necessary that they be reacted with leadalmost instantly after their formation. This is facilitated by the lowpressures at which I operate. Considerable quantities of uncondensed gaswill leave the cooler. I9 through line 22. Methane is one of the morecommon constituents of such gas and this hydrocarbon is decomposed bylead vapors with somewhat more difiiculty than hydrocarbons of highermolecular weight. Because of this fact I find it advantageous to recyclea portion of the uncondensed vapors back into the retort I where theuncondensed gas is introduced through pipe 25. This gas helps tovaporize the lead and conduct heat to pyrolysis zone 9.

Should there be an excessive accumulation of lead on the coolingelements in zone I0, I can remove it by momentarily interrupting theflow of cooling liquid therethrough.

Product obtained in 2I generally consists of a hydrocarbon solutioncontaining upwards of 0.5 to 2 percent of lead-hydrocarbon compounds.When gasoline is used as the source of hydrocarbon introduced throughinlet I3 the final product flowing from receiver 2| is an anti-knockblending fuel containing lead-hydrocarbon compounds asthe anti-knockconstituent. When I wish to prepare pure lead-hydrocarbon compounds itis better to use hydrocarbons which are normally gaseous, or which haverelatively low boiling points, somewhat lower than tetramethyl lead.When this is done condenser I9 can be so regulated that mainly thelead-hydrocarbon compounds collect in receiver 2I and effiuent unreactedhydrocarbon gases are recycled back to inlet I3.

Absorber 26 is advantageously used to recover any traces of uncondensedlead alkyls and also any uncondensed hydrocarbons such as butane orpentane. The absorption liquid, such as gas oil, flows out of theabsorber through line 26a and in through line 29. The liquid can be,distilled for the recovery of the dissolved constituents.

specifically recited in the foregoing description but it is understoodthat these are susceptible to modifications depending upon the kind ofhydrocarbon starting material. I find it best to work under lowpressures, of the order of to 4 mm. of mercury and rarely exceedingabout Operating conditions and pressures have been 50 mm. Gas flowthrough the reaction vessel must be rapid so that the free alkyls formedare cooled and contacted with lead almost instantaneously. Thecirculating pumps in the apparatus maintain the high velocity required.

1. In the process of preparing hydrocarbon compounds of lead by reactinglead with free alkyl radicals at a low subatmospheric pressure the stepswhich comprise pyrolytically dissociating a free alkyl-yieldinghydrocarbon by the action of highly heated vaporized lead and thenquickly cooling the mixture of lead vapor and free alkyls to atemperature below the decomposition temperature of the lead-hydrocarboncompounds.

2. In the process of preparing hydrocarbon compounds of lead by reactinglead with free alkyl radicals the steps which comprise. pyrolyticallydissociating a free alkyl-yielding hydrocarbon by the action of highlyheated vaporized lead at a pressure of about to 50 mm. ofmercuryabsolute and then quickly cooling the mixture of lead vapor and freealkyls at said pressure to a temperature below the decompositiontemperature of thelead-hydrocarbon compounds.

3. The process as in claim 2 wherein the pressure is about 2 to 4 mm. ofmercury absolute.

4. The process of preparing lead-hydrocarbon compounds which comprisesvaporizing metallic lead-hydrocarbon compounds.

5. The process as in claim 4 wherein the pressure is about to 4 mm. ofmercury absolute.

6. The process of preparing lead-hydrocarbon compounds which comprisesvaporizing metallic lead'at a low subatmospheric pressure, conductingthe lead vapor to a pyrolysis zone, introducing hydrocarbons-into saidzone, said hydrocar-- bons being capable of yielding free alkyl radicalson pyrolysis, whereby free alkyl radicals are formed, rapidly passingthe mixture of lead va-' par and free alkyl radicals into a cooling zonemaintained at a temperature below the decomposition temperature of thelead-hydrocarbon compounds, and condensing reaction products.

7. The process as in claim 6 wherein the pressure is about 2 to 4 mm. ofmercury absolute.

8. The process as in claim 1 wherein the hydrocarbon is gasoline.

9. The process as in claim 2 wherein the hydrocarbon is gasoline.

10. The process as in claim 4 wherein the hydrocarbon is gasoline.

11. The process as in claim 6 wherein the hydrocarbon is gasoline.

12. The process as in claim 2 wherein the hydrocarbon is gasoline. andthe pressure is about /2 to 4 mm. of mercury absolute.

13. The process as in claim 4 wherein the hy-' drocarbon is gasoline andthe pressure is about /2 to 4 mm. of mercury absolute.

14. The process as in claim 6 wherein the hydrocarbon is gasoline andthe pressure is about /2 to 4 mm. of mercury absolute.

FREDERICK W. SULLIVAN, JR.

